The two antibiotics fed in these four trials were Aureomycin and
Terramycin HCl at the level of 10 mg. per pound of total ration. Lot 1
pigs were the controls receiving the basal ration; Lot 2, basal plus
10 mg. of Aureomycin HCl per pound of total feed; Lot 3, basal plus
10 mg. of Terramycin HCl per pound of total feed. Fifty-two pigs
were used in the four trials carried out from November 1952 to October
1954.
The pigs were slaughtered at the college laboratory when they
reached approximately 225 pounds. The stomach and intestinal contents
were weighed and subtracted from the live slaughter weight to
determine the net body weight.
All carcasses were weighed after 48 hours chill at 34 ̊F. The
length of body was measured from the anterior portion of the first
rib to the anterior portion of the aitch bone. The back fat is the
average of the three measurements-opposite the first rib, last rib, and
last lumbar vertebra. The primal cuts are the skinned ham, trimmed
loin, N.Y. style shoulder, and the trimmed belly. The lean cuts are the
skinned ham, trimmed loin, and N.Y. style shoulder. The primal and
lean-cut yields were based on net body weight and chilled carcass
weight. The carcasses were graded, using the average back fat thickness
and length as criteria for grades. These grades are based on the
official U.S. Standards for Grades of Pork Carcasses, which are choice
1, 2, 3; medium; and cull.